Themodynamic and transport properties of intermediate states of the photocyclic reaction of photoactive yellow protein.
Themodynamic and transport properties of intermediate states of the photocyclic reaction of photoactive yellow protein.
复制标题
DOI：
10.1021/bi0110600
复制
发表时间：
2002-02
期刊：
影响因子：
2.9
通讯作者：
K. Takeshita;Y. Imamoto;M. Kataoka;F. Tokunaga;M. Terazima
中科院分区：
文献类型：
--
作者：
K. Takeshita;Y. Imamoto;M. Kataoka;F. Tokunaga;M. Terazima
利用脉冲激光诱导瞬态光栅（TG）、瞬态透镜（TrL）和光声（PA）光谱技术研究了光敏黄蛋白（PYP）光环化反应中间态的热力学和输运性质。通过TG分析测定了PYP在基态（pG）和第二中间态（pB）的扩散系数（D），发现pG的D约为pB的D的1.2倍。同时，以盐酸胍为变性剂，测定了不同变性条件下的D值。完全未折叠的蛋白质的D约为天然形式的0.4倍。用TrL方法估算了pB的焓为60 kJ/mol，并假设pB的体积变化对温度不敏感。由于第一中间态（pR）的焓高达160 kJ/mol，这意味着大部分光子能量作为蛋白质的应变储存在pR中，这可能是连续反应到pB的驱动力。从体积变化的温度依赖性，计算pG和pR之间的热膨胀系数的差异。PYP的所有特征，负体积变化，较大的热膨胀系数，和较慢的扩散过程，表明中间的pR和pB是合理的解释展开（松散）的蛋白质结构。
Themodynamic and transport properties of intermediate states of the photocyclic reaction of photoactive yellow protein (PYP) were studied by a combination of the pulsed laser-induced transient grating (TG), transient lens (TrL), and photoacoustic (PA) spectroscopies from tens of nanoseconds to hundreds of milliseconds. The diffusion coefficients (D) of PYP in the ground state (pG) and of the second intermediate state (pB) were determined by the TG analysis, and it was found that D of pG is about 1.2 times larger than D of pB. At the same time, D at various denatured conditions were measured using guanidine hydrochloride as the denaturant. D of completely unfolded protein is about 0.4 times that of the native form. The enthalpy of pB is estimated to be 60 kJ/mol by the TrL method with an assumption that the volume change of pB is not sensitive to the temperature. Since the enthalpy of the first intermediate state (pR) is as high as 160 kJ/mol, it implies that most of the photon energy is stored as the strain of the protein in pR, and this may be the driving force for the successive reaction to pB. From the temperature dependence of the volume change, the difference in the thermal expansion coefficients between pG and pR was calculated. All of the characteristic features of PYP, the negative volume change, the larger thermal expansion coefficient, and the slower diffusion process, indicate that the intermediate pR and pB are reasonably interpreted in terms of the unfolded (loosened) protein structure.